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Hot end concerns

Posted by antimix 
Hot end concerns
March 23, 2013 04:23PM

I am trying to finish to mount my RepRapPro. I am at the extruder hot end.
I have some questions for people with more experience than me:

1) From the installation instructions, I am concerned that the extruder cable that brings power to the hot end resistor, after a few centimeters of cable and connector, become a PC ribbon flat !
Picture: Hotend connected to ribbon flat

- Has really a ribbon flat the capability to support all the power for the hot resistor or it will become hot ?

2) Both terminals of the hot end resistor and thermistore should be crimped with JST stating the instructions.
I am not able to ensure a good crimp, since I do not have the correct micro crimp tool for 1.2 mm JST female.
Picture: Thermistore Crimped and Resistor not yet

Of course I can order one and wait a couple of weeks.

- Is it the same, if I fix the cable with solder without crimp, or the hot end high temperature will melt the solder ?

This is my first attempt to mount a RepRap printer, and there is no day that I can find a small problem (e.g. no correct screw, screws head to file, shrink with hot air and no gun....), and I solve them patiently. I love it, because it gives more satisfaction once the printer is ended.

In this case I do not have idea what could be the correct approach. Any suggetions ?

Best Regards
Re: Hot end concerns
March 23, 2013 06:51PM
You want to avoid soldering the hotend resistor, it's usually an area that gets hot enough to erode the solder over time often leading to failure of the joint later, usually when most inconvenient.
You should be able to get a decent crimp with a pair of pliers.
Re: Hot end concerns
March 23, 2013 08:50PM
You don't have to buy a special crimping tool for those connectors. I crimp them with a pair of needle nose pliers.I fold each side into the wire one at a time.
Anonymous User
Re: Hot end concerns
March 23, 2013 09:45PM
Definitely get a pair of the speciality crimpers. If you do them with needle nose pliers, they will eventually loosen and disconnect. I bought a pair from Pololu. http://www.pololu.com/catalog/product/1929 They work great.

As long as the solder is outside the hot end bundle, and the hot end stays below 300C or so, soldering your wires to the resistors should be ok.

As far as the flat ribbon cable, I'd recommend teflon coated 22 gauge wire from McMaster-Carr, product# 7304K112
Re: Hot end concerns
March 23, 2013 09:58PM
For what it's worth, I have soldered the wires onto 2 heating resistors and have had zero issues with the joints failing over many hundreds of hours of printing.

I left the leads their full length on the resistor, and the joints are insulated separately from the body of the hotend.
Re: Hot end concerns
March 24, 2013 12:26AM

Definitely get a pair of the speciality crimpers. If you do them with needle nose pliers, they will eventually loosen and disconnect. ...

Not necessarily. I crimped all the pins in 3 printers (Mendel over 2 years ago, Prusa2 a year ago and Ordbot Hadron a couple of months) with pliers and not a single one has come loose. I've been making connectors in this way for many years. Using a crimper does samve time so if you do it often, it's worth getting one.
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